1. Field of the Invention
The present invention relates generally to medical apparatus and methods for using such apparatus. In particular, the present invention relates to systems and methods for accessing target locations in or through natural and created body lumens.
A wide variety of catheters and probes are used in an almost unlimited number of medical procedures and protocols. Of particular interest herein, tubular catheters are often used to provide access through body lumens, for example, through a patient's urethral canal to permit draining the bladder. Such catheters are typically referred to as urinary catheters and are inserted into the bladder via the urethra. Ureteral catheters can be inserted into the ureter via the bladder to reach the kidneys. The catheters can have a variety of purposes, including access to/capture of and/or destruction of urinary calculi. The introduction of such urinary and uretal catheters is often the cause of urinary infections. For example, the introduction of urinary catheters into the urethra can carry bacteria or other infections materials from the patient's skin or the lower urinary tract into the bladder or from the bladder into the upper urinary tract. The leading tip of such conventional catheters can act as a pusher or transfer device that can unintentionally spread infection.
Even if proper precautions are taken to reduce or eliminate infection, the advancement of conventional catheters through the urethra, ureter, or other small body lumens can irritate the luminal wall and cause discomfort or, in the worst cases, injury to the walls. Even if no serious damage is caused, the resulting scarring can lead to stricture formation and discomfort can be substantial.
To overcome both of these problems, RTC, Inc. of St. Paul, Minn., has developed the Memcath™ Intermittent Urology Catheter which uses a PTFE sheath which everts from the interior of the catheter over the exterior as the catheter is introduced. As illustrated in FIG. 1, the Memcath™ catheter 10 has a tubular PTFE membrane 12 which is initially stowed within the lumen 14 of the catheter. The membrane extends out a distal end of the catheter 10 and has an everting section 18 which attaches to a ring 20 which can slide over the exterior surface of the catheter. In this way, as the catheter 10 is advanced into a body lumen, such as the urethra, the tubular membrane 10 will be pulled around the distal end 16 of the catheter to cover the exterior of the catheter as it advances. Since the ring 20 is held stationary relative to the body lumen, the membrane, once it is deployed, will also remain stationary, reducing the risk of trauma to the luminal wall and preventing the propagation of bacteria and other pathogens upward into the body lumen.
While this design is fundamentally sound, it does suffer from certain shortcomings. The ring 20 is intended to be held manually over the access orifice of the body lumen. Thus, the Memcath™ catheter is suitable for introduction through the urethra, but would be difficult to deploy in the ureter or other internal body lumen, particularly using an endoscope or other minimally invasive approach. The distal end of the catheter 10 is relatively stiff, so introduction of the catheter through a relatively tortuous path and/or past obstructing material, such as urinary calculi, can be difficult. Additionally, if the membrane 12 is not fully deployed, a trailing end can remain within the lumen 14 of the catheter, making access through the lumen difficult.
For these reasons, it would be desirable to provide improved designs and methods of use for luminal access catheters of the type which include a protective, deployable outer membrane. In particular, it would be desirable to provide such catheters which are suitable for endoscopic and other minimally invasive deployments. It would further be desirable to provide such catheters having relatively flexible or deflectable distal ends to permit introduction into relatively tortuous lumens and/or introduction past obstructing materials within such lumens. It would further be desirable if the catheters were suitable for introduction over guidewires in at least some circumstances. Additionally, it would be desirable to provide such catheters which maintain an open lumen, even if the protective sheath is not fully deployed while the catheter is introduced. It would be further desirable if the membrane position could be reset after use to allow multiple advancements with the same catheter in a single patient. At least some of these objectives will be met by the inventions described below.
2. Description of the Background Art
The use of an everting sleeve composed of thin, tensilized polytetrafluoroethylene for introducing catheters to body lumens is described in U.S. Pat. Nos. 5,531,717; 5,676,688; 5,711,841; 5,897,535; 6,007,488; 6,240,968; and EP605427B1. Other catheters employing everting sleeves for a variety of purposes are described in commonly assigned, copending application Ser. Nos. 10/794,337, filed on Mar. 5, 2004, Ser. No. 10/794,317, filed on Mar. 5, 2004, and Ser. No. 10/886,886, filed on Jul. 7, 2004, the full disclosures of which are incorporated herein by reference.